Thermally heated seats are disclosed in several prior patents. For example, see U.S. Pat. Nos. 5,545,198; 5,700,284; 5,300,105; 5,357,693; and D343,088, all of which are assigned to Vesture Corporation, the assignee of the above-identified application. These patents generally describe seat cushions which include a removable envelope enclosing a fluid which can be heated in a microwave oven.
It is well known that liquid-containing heating pads are designed to heat parts of the human body to help heal injuries, alleviate soreness, and provide comfort in cold environments. Heating pads may be conventional hot water bottles, which can be filled with heated liquid, or may be modern, sealed liquid pouches, which can be heated by microwave energy. In recent years, heating pads of flexible plastic envelopes containing water-based solutions have been manufactured and sold. Such pads are manufactured by placing them in a vacuum pump and evacuating the air within the envelopes. The envelopes are then heat sealed with the liquid therein. Certain microwavable heating pads tend to retain heat for up to several hours, depending on their design.
Portable seat cushions are popular accessories for concert spectators, sports fans, campers, fisherman, and outdoor enthusiasts in general. Heating pads have been installed inside seat cushions to keep spectators and the like warm when using the seat cushions in cold conditions. A seat cushion having a removable heating pad for easy heating in a microwave oven is described in U.S. Pat. No. 5,545,198 to Owens. Certain other prior art seat cushions include heating pads which often do not remain in the centers of the cushions, which is where the heating pads function most effectively. A comfortable back rest is also often lacking in certain prior art seat cushions.